* ext/weak: new weakref implementation.

ext/weak/extconf.rb

@@ -0,0 +1,2 @@
+require "mkmf"
+create_makefile("weak")

ext/weak/weak.c

@@ -0,0 +1,127 @@
+#include "ruby.h"
+
+struct weak_object {
+    VALUE obj;
+    VALUE queue;
+};
+
+#define WOBJ_FINALIZED ((struct weak_object *)-1)
+#define WOBJ_VALID_P(wh) ((wh) && (wh) != WOBJ_FINALIZED)
+
+static void
+wobj_mark(void *p)
+{
+    struct weak_object *wh = p;
+    if (!WOBJ_VALID_P(wh)) return;
+    if (!NIL_P(wh->queue)) rb_gc_mark(wh->queue);
+}
+
+static void
+wobj_free(void *p)
+{
+    struct weak_object *wh = p;
+    if (WOBJ_VALID_P(wh)) {
+	VALUE obj = wh->obj;
+	if (!NIL_P(obj)) rb_undefine_finalizer(obj);
+    }
+}
+
+static size_t
+wobj_memsize(const void *p)
+{
+    return p ? sizeof(struct weak_object) : 0;
+}
+
+static const rb_data_type_t weakobject_type = {
+    "weakobject",
+    {
+	wobj_mark,
+	wobj_free,
+	wobj_memsize,
+    },
+    NULL, NULL, RUBY_TYPED_FREE_IMMEDIATELY,
+};
+
+static VALUE
+wobj_allocate(VALUE klass)
+{
+    return TypedData_Wrap_Struct(klass, &weakobject_type, NULL);
+}
+
+static VALUE
+wobj_deref(VALUE wobj)
+{
+    struct weak_object *wh = DATA_PTR(wobj);
+    return WOBJ_VALID_P(wh) ? wh->obj : Qnil;
+}
+
+static VALUE
+wobj_alive_p(VALUE wobj)
+{
+    struct weak_object *wh = DATA_PTR(wobj);
+    return WOBJ_VALID_P(wh) ? Qtrue : Qfalse;
+}
+
+static VALUE
+wobj_initialize(int argc, VALUE *argv, VALUE wobj)
+{
+    VALUE obj, queue;
+    struct weak_object *wh;
+
+    rb_scan_args(argc, argv, "11", &obj, &queue);
+
+    if (DATA_PTR(wobj)) {
+	rb_raise(rb_eArgError, "already initialized");
+    }
+    while (rb_typeddata_is_kind_of(obj, &weakobject_type)) {
+	obj = wobj_deref(obj);
+    }
+    DATA_PTR(wobj) = wh = ALLOC(struct weak_object);
+    rb_define_finalizer(obj, wobj);
+    wh->obj = obj;
+    wh->queue = queue;
+    return wobj;
+}
+
+static VALUE
+wobj_finalize(int argc, VALUE *argv, VALUE wobj)
+{
+    struct weak_object *wh = DATA_PTR(wobj);
+    if (WOBJ_VALID_P(wh)) {
+	VALUE queue = wh->queue;
+	DATA_PTR(wobj) = WOBJ_FINALIZED;
+	xfree(wh);
+	if (!NIL_P(queue)) {
+	    rb_funcallv(queue, rb_intern("push"), 1, &wobj);
+	}
+    }
+    return Qnil;
+}
+
+static VALUE
+wobj_inspect(VALUE wobj)
+{
+    VALUE str = rb_any_to_s(wobj);
+    struct weak_object *wh = DATA_PTR(wobj);
+    VALUE obj;
+    if (WOBJ_VALID_P(wh) && !NIL_P(obj = wh->obj)) {
+	rb_str_set_len(str, RSTRING_LEN(str)-1);
+	rb_str_cat2(str, ": ");
+	rb_str_append(str, rb_inspect(wh->obj));
+	rb_str_cat2(str, ">");
+    }
+    return str;
+}
+
+void
+Init_weak(void)
+{
+    VALUE rb_cWeakObject = rb_define_class("Weak", rb_cObject);
+    rb_define_alloc_func(rb_cWeakObject, wobj_allocate);
+    rb_define_singleton_method(rb_cWeakObject, "ref", rb_class_new_instance, -1);
+    rb_define_private_method(rb_cWeakObject, "call", wobj_finalize, -1);
+    rb_define_method(rb_cWeakObject, "initialize", wobj_initialize, -1);
+    rb_define_method(rb_cWeakObject, "get", wobj_deref, 0);
+    rb_define_method(rb_cWeakObject, "alive?", wobj_alive_p, 0);
+    rb_define_method(rb_cWeakObject, "inspect", wobj_inspect, 0);
+}

test/weak/test_weak_ref.rb

@@ -0,0 +1,61 @@
+require 'test/unit'
+require 'weak'
+require_relative '../ruby/envutil'
+
+class TestWeakRef < Test::Unit::TestCase
+  def make_weakref(*args, level: 10)
+    if level > 0
+      make_weakref(*args, level: level-1)
+    else
+      args <<= Object.new if args.empty?
+      Weak.ref(*args)
+    end
+  ensure
+    args.clear
+  end
+
+  def test_ref
+    obj = Object.new
+    weak = Weak.ref(obj)
+    assert_same(obj, weak.get)
+    assert_predicate(weak, :alive?)
+  end
+
+  def test_recycled
+    weak = 1.times {break make_weakref}
+    GC.start
+    GC.start
+    assert_nil(weak.get)
+    assert_not_predicate(weak, :alive?)
+  end
+
+  def test_finalize
+    bug7304 = '[ruby-core:49044]'
+    assert_normal_exit %q{
+      require 'weak'
+      obj = Object.new
+      3.times do
+        Weak.ref(obj)
+        ObjectSpace.garbage_collect
+      end
+    }, bug7304
+  end
+
+  def test_queue
+    q = Object.new
+    def q.pushed; @pushed; end
+    def q.push(obj); @pushed = obj; end
+
+    ref = nil
+    1.times do
+      o = Object.new
+      ref = make_weakref(o, q)
+      assert_same(o, ref.get)
+      assert_nil(q.pushed)
+    end
+
+    5.times { GC.start }
+    assert_nil(ref.get)
+    assert_same(ref, q.pushed)
+  end
+end